When fabricating optical components such as lenses, it is very common to form a coating on a surface of the component, where the coating provides desired optical or physical properties. For example, the coating may provide an antireflective (AR) characteristic, a filtering characteristic, physical protection for the component, some other characteristic, or a combination of two or more characteristics. These coatings often include multiple layers of different materials that collectively provide the desired characteristic(s).
One problem with conventional coating techniques is that any given layer in the coating may have a thickness that is not uniform throughout the layer. For example, where a coating is formed on a relatively highly curved surface, it is common for a given layer within the coating to have a peripheral region that is as much as 30% to 50% thinner than a central region of that layer, or even more than 50% thinner. Further, different layers in the same coating often have different variations in thickness. For example, one layer may be 30% thinner in a peripheral region than in a central region, while another layer may be 50% thinner in the peripheral region than in the central region. Consequently, the ratios of thicknesses of different layers in the peripheral region can be different from the ratios of thicknesses of those same layers in the central region.
Thus, even assuming that the layers of a coating all have the proper thicknesses or proper ratios of thicknesses in the central region, the thicknesses in the peripheral region will typically not be correct and, moreover, the ratios of thicknesses in the peripheral region will typically not be correct. As a result, the coating should provide the desired characteristics in its central region, but may fail to provide the desired characteristics in its peripheral region, or may at least exhibit a degradation of the desired characteristics in the peripheral region.